When Brendan Cowan boarded the 8:05 a.m. ferry at Friday Harbor, Wash., one day late last month, there was a little something extra waiting for him and his fellow passengers at the end of the the route in Anacortes, courtesy of the U.S. Border Patrol.

On that day, all vehicles were channeled through lanes normally reserved for international travelers so that Border Patrol agents could ask if they were U.S. citizens.

Islanders are used to being routed through Customs when they board vessels that had originated in British Columbia. But Cowan's ride on Jan. 24 was a domestic run, and in seven years of island living he had never before encountered it.

"They didn't ask me to produce proof," Cowan recalled, who affirmed he was American, and was then waved through. The agent "called it a 'citizen check.'"

The short-lived checkpoint did not stem from any specific information regarding a threat but, rather, was "part of a comprehensive tactical portfolio," according to Blaine-based Border Patrol spokesperson Joe Giuliano. Anacortes, he said, is a location with "a history of individuals and/or contraband arriving illegally on the islands and using this particular ferry run to further their entry to the mainland."

Giuliano said he has received several media inquiries and a number of calls from citizens regarding the screening. He described all the citizen calls as "neutral or positive."

That may not be a completely accurate description, though, of how citizens actually felt. One islander who asked for anonymity said, "Everyone I've talked to here sees it as a bit shocking and surprising."

In addition, the American Civil Liberties Union of Washington said it has received a complaint "from at least one person."

Giuliano said his agency had previously staged similar checkpoints at Anacortes on domestic runs, and that it routinely gives advance notice to state ferry officials.

But Washington State Ferries spokesperson Susan Harris-Huether said the state has no record of the Border Patrol informing them about last month's surprise appearance. They "simply showed up," said Harris-Huether, adding that ferry personnel in Anacortes also told her they had "no record of them having previously done this for domestic traffic – they don't remember this happening before."

That squares with the feedback Cowan sought after he emailed some 20 island buddies who have collectively lived on the island about 350 years. Without exception, no one could recall a similar screening at Anacortes for a domestic sailing, he said.

While Cowan and some other islanders consider the Border Patrol's sudden appearance noteworthy, they're not disputing the agency's right to set up such checkpoints.

ACLU spokesman Doug Honig said ACLU lawyers would need to know more about what happened before determining if it was legal. He added, "People who feel they are being unfairly stopped can verbally register a protest about the questioning, and it's usually wise to do so politely."

According to Giuliano:

The courts have long held that such checkpoints, no matter the manner of conveyance involved, are legal and proper so long as some essential conditions are met. Among them are that there must be a nexus to the international border; that they must be on a route that leads from the area of the border; and that they cannot be arbitrary – that is, everyone must be inspected, not just some of the travelers at the whim of the agent.

Still, Giuliano acknowledged that U.S. citizens are not obliged to carry any identification inside the country. Border Patrol agents cannot demand proof of citizenship from ferry passengers, he said, as long as they have "no reason to doubt the veracity" of their statements that they are U.S. citizens.

Asked what criteria Border Patrol agents use to determine whether a passenger's answer is credible, Giuliano said:

Agents use a combination of training-reinforced intuition, an institutional knowledge of their job and work environment, and a recognition of specific behaviors. Unfortunately, I cannot provide more specific information for publication as this would provide a tactical advantage to those of your readers who may be inclined to circumvent the law.

No one was arrested, and no contraband was seized as a result of last month's surprise screening at Anacortes, Giuliano said. He added that such checks "are intermittent and will continue. We do not publicize the precise times and dates because doing so would work to the advantage of those seeking to circumvent the law. The frequency with which we run ferry checks is determined primarily by operational need, resource availability and prioritization within our tactical portfolio."